Hey Ian,
I don't have a lot of experience with rime, but I have climbed on it when it would support body weight, like stemming between feathers, and obviously this is the most positive.
Most of the time it won't support shit. The best method I have found in this case is to punch through the outer layer into the sugar under the rime, push my tools in horizontally grabbing the tool by the head, and rotate the shaft downward using my wrist. Then it is a manteling motion to make vertical gain. This obviously becomes difficult when steeper then 80 degrees, and can be off balance, so serious trenching may be required.
For gear, not much works more than psychologically, but you can chop threads, scratch down to the rock if the rime isn't thick, or use screws in the few spots this may form. Creativity, and hard thickheaded work seem to be your best friend on this kind of climbing.
These same techniques also work for flutings. Good luck with round 2 on your climb!